How To Make Gui Apps Based On C Programming Language

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Walkthrough: Create a traditional Windows Desktop application (C++)

10/29/2021
14 minutes to read

This walkthrough shows how to create a traditional Windows desktop application in Visual Studio. The example application you'll create uses the Windows API to display "Hello, Windows desktop!" in a window. You can use the code that you develop in this walkthrough as a pattern to create other Windows desktop applications.

The Windows API (also known as the Win32 API, Windows Desktop API, and Windows Classic API) is a C-language-based framework for creating Windows applications. It has been in existence since the 1980s and has been used to create Windows applications for decades. More advanced and easier-to-program frameworks have been built on top of the Windows API. For example, MFC, ATL, the .NET frameworks. Even the most modern Windows Runtime code for UWP and Store apps written in C++/WinRT uses the Windows API underneath. For more information about the Windows API, see Windows API Index. There are many ways to create Windows applications, but the process above was the first.

Important

For the sake of brevity, some code statements are omitted in the text. The Build the code section at the end of this document shows the complete code.

Prerequisites

A computer that runs Microsoft Windows 7 or later versions. We recommend Windows 10 or later for the best development experience.
A copy of Visual Studio. For information on how to download and install Visual Studio, see Install Visual Studio. When you run the installer, make sure that the Desktop development with C++ workload is checked. Don't worry if you didn't install this workload when you installed Visual Studio. You can run the installer again and install it now.
An understanding of the basics of using the Visual Studio IDE. If you've used Windows desktop apps before, you can probably keep up. For an introduction, see Visual Studio IDE feature tour.
An understanding of enough of the fundamentals of the C++ language to follow along. Don't worry, we don't do anything too complicated.

Create a Windows desktop project

Follow these steps to create your first Windows desktop project. As you go, you'll enter the code for a working Windows desktop application. To see the documentation for your preferred version of Visual Studio, use the Version selector control. It's found at the top of the table of contents on this page.

To create a Windows desktop project in Visual Studio

From the main menu, choose File > New > Project to open the Create a New Project dialog box.
At the top of the dialog, set Language to C++, set Platform to Windows, and set Project type to Desktop.
From the filtered list of project types, choose Windows Desktop Wizard then choose Next. In the next page, enter a name for the project, for example, DesktopApp.
Choose the Create button to create the project.
The Windows Desktop Project dialog now appears. Under Application type, select Desktop application (.exe). Under Additional options, select Empty project. Choose OK to create the project.
In Solution Explorer, right-click the DesktopApp project, choose Add, and then choose New Item.
In the Add New Item dialog box, select C++ File (.cpp). In the Name box, type a name for the file, for example, HelloWindowsDesktop.cpp. Choose Add.

Your project is now created and your source file is opened in the editor. To continue, skip ahead to Create the code.

To create a Windows desktop project in Visual Studio 2017

On the File menu, choose New and then choose Project.
In the New Project dialog box, in the left pane, expand Installed > Visual C++, then select Windows Desktop. In the middle pane, select Windows Desktop Wizard.

In the Name box, type a name for the project, for example, DesktopApp. Choose OK.
In the Windows Desktop Project dialog, under Application type, select Windows application (.exe). Under Additional options, select Empty project. Make sure Precompiled Header isn't selected. Choose OK to create the project.
In Solution Explorer, right-click the DesktopApp project, choose Add, and then choose New Item.
In the Add New Item dialog box, select C++ File (.cpp). In the Name box, type a name for the file, for example, HelloWindowsDesktop.cpp. Choose Add.

Your project is now created and your source file is opened in the editor. To continue, skip ahead to Create the code.

To create a Windows desktop project in Visual Studio 2015

On the File menu, choose New and then choose Project.
In the New Project dialog box, in the left pane, expand Installed > Templates > Visual C++, and then select Win32. In the middle pane, select Win32 Project.

In the Name box, type a name for the project, for example, DesktopApp. Choose OK.
On the Overview page of the Win32 Application Wizard, choose Next.
On the Application Settings page, under Application type, select Windows application. Under Additional options, uncheck Precompiled header, then select Empty project. Choose Finish to create the project.
In Solution Explorer, right-click the DesktopApp project, choose Add, and then choose New Item.
In the Add New Item dialog box, select C++ File (.cpp). In the Name box, type a name for the file, for example, HelloWindowsDesktop.cpp. Choose Add.

Your project is now created and your source file is opened in the editor.

Create the code

Next, you'll learn how to create the code for a Windows desktop application in Visual Studio.

To start a Windows desktop application

Just as every C application and C++ application must have a main function as its starting point, every Windows desktop application must have a WinMain function. WinMain has the following syntax.
```
                int WINAPI WinMain(    _In_ HINSTANCE hInstance,    _In_opt_ HINSTANCE hPrevInstance,    _In_ LPSTR     lpCmdLine,    _In_ int       nCmdShow );                              
```
For information about the parameters and return value of this function, see WinMain entry point.

Note

What are all those extra words, such as WINAPI, or CALLBACK, or HINSTANCE, or _In_? The traditional Windows API uses typedefs and preprocessor macros extensively to abstract away some of the details of types and platform-specific code, such as calling conventions, __declspec declarations, and compiler pragmas. In Visual Studio, you can use the IntelliSense Quick Info feature to see what these typedefs and macros define. Hover your mouse over the word of interest, or select it and press Ctrl+K, Ctrl+I for a small pop-up window that contains the definition. For more information, see Using IntelliSense. Parameters and return types often use SAL Annotations to help you catch programming errors. For more information, see Using SAL Annotations to Reduce C/C++ Code Defects.
Windows desktop programs require <windows.h>. <tchar.h> defines the TCHAR macro, which resolves ultimately to wchar_t if the UNICODE symbol is defined in your project, otherwise it resolves to char . If you always build with UNICODE enabled, you don't need TCHAR and can just use wchar_t directly.
```
                #include <windows.h> #include <tchar.h>                              
```
Along with the WinMain function, every Windows desktop application must also have a window-procedure function. This function is typically named WndProc, but you can name it whatever you like. WndProc has the following syntax.
```
                LRESULT CALLBACK WndProc(    _In_ HWND   hWnd,    _In_ UINT   message,    _In_ WPARAM wParam,    _In_ LPARAM lParam );                              
```
In this function, you write code to handle messages that the application receives from Windows when events occur. For example, if a user chooses an OK button in your application, Windows will send a message to you and you can write code inside your WndProc function that does whatever work is appropriate. It's called handling an event. You only handle the events that are relevant for your application.

For more information, see Window Procedures.

To add functionality to the WinMain function

In the WinMain function, you populate a structure of type WNDCLASSEX. The structure contains information about the window: the application icon, the background color of the window, the name to display in the title bar, among other things. Importantly, it contains a function pointer to your window procedure. The following example shows a typical WNDCLASSEX structure.

                WNDCLASSEX wcex;  wcex.cbSize         = sizeof(WNDCLASSEX); wcex.style          = CS_HREDRAW | CS_VREDRAW; wcex.lpfnWndProc    = WndProc; wcex.cbClsExtra     = 0; wcex.cbWndExtra     = 0; wcex.hInstance      = hInstance; wcex.hIcon          = LoadIcon(wcex.hInstance, IDI_APPLICATION); wcex.hCursor        = LoadCursor(NULL, IDC_ARROW); wcex.hbrBackground  = (HBRUSH)(COLOR_WINDOW+1); wcex.lpszMenuName   = NULL; wcex.lpszClassName  = szWindowClass; wcex.hIconSm        = LoadIcon(wcex.hInstance, IDI_APPLICATION);

For information about the fields of the structure above, see WNDCLASSEX.

Register the WNDCLASSEX with Windows so that it knows about your window and how to send messages to it. Use the RegisterClassEx function and pass the window class structure as an argument. The _T macro is used because we use the TCHAR type.

                if (!RegisterClassEx(&wcex)) {    MessageBox(NULL,       _T("Call to RegisterClassEx failed!"),       _T("Windows Desktop Guided Tour"),       NULL);     return 1; }

Now you can create a window. Use the CreateWindowEx function.

                static TCHAR szWindowClass[] = _T("DesktopApp"); static TCHAR szTitle[] = _T("Windows Desktop Guided Tour Application");  // The parameters to CreateWindowEx explained: // WS_EX_OVERLAPPEDWINDOW : An optional extended window style. // szWindowClass: the name of the application // szTitle: the text that appears in the title bar // WS_OVERLAPPEDWINDOW: the type of window to create // CW_USEDEFAULT, CW_USEDEFAULT: initial position (x, y) // 500, 100: initial size (width, length) // NULL: the parent of this window // NULL: this application does not have a menu bar // hInstance: the first parameter from WinMain // NULL: not used in this application HWND hWnd = CreateWindowEx( WS_EX_OVERLAPPEDWINDOW,    szWindowClass,    szTitle,    WS_OVERLAPPEDWINDOW,    CW_USEDEFAULT, CW_USEDEFAULT,    500, 100,    NULL,    NULL,    hInstance,    NULL ); if (!hWnd) {    MessageBox(NULL,       _T("Call to CreateWindowEx failed!"),       _T("Windows Desktop Guided Tour"),       NULL);     return 1; }

This function returns an HWND, which is a handle to a window. A handle is somewhat like a pointer that Windows uses to keep track of open windows. For more information, see Windows Data Types.

At this point, the window has been created, but we still need to tell Windows to make it visible. That's what this code does:
```
                // The parameters to ShowWindow explained: // hWnd: the value returned from CreateWindow // nCmdShow: the fourth parameter from WinMain ShowWindow(hWnd,    nCmdShow); UpdateWindow(hWnd);                              
```
The displayed window doesn't have much content because you haven't yet implemented the WndProc function. In other words, the application isn't yet handling the messages that Windows is now sending to it.

To handle the messages, we first add a message loop to listen for the messages that Windows sends. When the application receives a message, this loop dispatches it to your WndProc function to be handled. The message loop resembles the following code.

                MSG msg; while (GetMessage(&msg, NULL, 0, 0)) {    TranslateMessage(&msg);    DispatchMessage(&msg); }  return (int) msg.wParam;

For more information about the structures and functions in the message loop, see MSG, GetMessage, TranslateMessage, and DispatchMessage.

At this point, the WinMain function should resemble the following code.

                int WINAPI WinMain(HINSTANCE hInstance,                    HINSTANCE hPrevInstance,                    LPSTR lpCmdLine,                    int nCmdShow) {    WNDCLASSEX wcex;     wcex.cbSize = sizeof(WNDCLASSEX);    wcex.style          = CS_HREDRAW | CS_VREDRAW;    wcex.lpfnWndProc    = WndProc;    wcex.cbClsExtra     = 0;    wcex.cbWndExtra     = 0;    wcex.hInstance      = hInstance;    wcex.hIcon          = LoadIcon(wcex.hInstance, IDI_APPLICATION);    wcex.hCursor        = LoadCursor(NULL, IDC_ARROW);    wcex.hbrBackground  = (HBRUSH)(COLOR_WINDOW+1);    wcex.lpszMenuName   = NULL;    wcex.lpszClassName  = szWindowClass;    wcex.hIconSm        = LoadIcon(wcex.hInstance, IDI_APPLICATION);     if (!RegisterClassEx(&wcex))    {       MessageBox(NULL,          _T("Call to RegisterClassEx failed!"),          _T("Windows Desktop Guided Tour"),          NULL);        return 1;    }     // Store instance handle in our global variable    hInst = hInstance;     // The parameters to CreateWindowEx explained:    // WS_EX_OVERLAPPEDWINDOW : An optional extended window style.    // szWindowClass: the name of the application    // szTitle: the text that appears in the title bar    // WS_OVERLAPPEDWINDOW: the type of window to create    // CW_USEDEFAULT, CW_USEDEFAULT: initial position (x, y)    // 500, 100: initial size (width, length)    // NULL: the parent of this window    // NULL: this application dows not have a menu bar    // hInstance: the first parameter from WinMain    // NULL: not used in this application    HWND hWnd = CreateWindowEx(       WS_EX_OVERLAPPEDWINDOW,       szWindowClass,       szTitle,       WS_OVERLAPPEDWINDOW,       CW_USEDEFAULT, CW_USEDEFAULT,       500, 100,       NULL,       NULL,       hInstance,       NULL    );     if (!hWnd)    {       MessageBox(NULL,          _T("Call to CreateWindow failed!"),          _T("Windows Desktop Guided Tour"),          NULL);        return 1;    }     // The parameters to ShowWindow explained:    // hWnd: the value returned from CreateWindow    // nCmdShow: the fourth parameter from WinMain    ShowWindow(hWnd,       nCmdShow);    UpdateWindow(hWnd);     // Main message loop:    MSG msg;    while (GetMessage(&msg, NULL, 0, 0))    {       TranslateMessage(&msg);       DispatchMessage(&msg);    }     return (int) msg.wParam; }

To add functionality to the WndProc function

To enable the WndProc function to handle the messages that the application receives, implement a switch statement.

One important message to handle is the WM_PAINT message. The application receives the WM_PAINT message when part of its displayed window must be updated. The event can occur when a user moves a window in front of your window, then moves it away again. Your application doesn't know when these events occur. Only Windows knows, so it notifies your app with a WM_PAINT message. When the window is first displayed, all of it must be updated.

To handle a WM_PAINT message, first call BeginPaint, then handle all the logic to lay out the text, buttons, and other controls in the window, and then call EndPaint. For the application, the logic between the beginning call and the ending call displays the string "Hello, Windows desktop!" in the window. In the following code, the TextOut function is used to display the string.
```
                PAINTSTRUCT ps; HDC hdc; TCHAR greeting[] = _T("Hello, Windows desktop!");  switch (message) { case WM_PAINT:    hdc = BeginPaint(hWnd, &ps);     // Here your application is laid out.    // For this introduction, we just print out "Hello, Windows desktop!"    // in the top left corner.    TextOut(hdc,       5, 5,       greeting, _tcslen(greeting));    // End application-specific layout section.     EndPaint(hWnd, &ps);    break; }                              
```
HDC in the code is a handle to a device context, which is used to draw in the window's client area. Use the BeginPaint and EndPaint functions to prepare for and complete the drawing in the client area. BeginPaint returns a handle to the display device context used for drawing in the client area; EndPaint ends the paint request and releases the device context.

An application typically handles many other messages. For example, WM_CREATE when a window is first created, and WM_DESTROY when the window is closed. The following code shows a basic but complete WndProc function.

                LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam) {    PAINTSTRUCT ps;    HDC hdc;    TCHAR greeting[] = _T("Hello, Windows desktop!");     switch (message)    {    case WM_PAINT:       hdc = BeginPaint(hWnd, &ps);        // Here your application is laid out.       // For this introduction, we just print out "Hello, Windows desktop!"       // in the top left corner.       TextOut(hdc,          5, 5,          greeting, _tcslen(greeting));       // End application specific layout section.        EndPaint(hWnd, &ps);       break;    case WM_DESTROY:       PostQuitMessage(0);       break;    default:       return DefWindowProc(hWnd, message, wParam, lParam);       break;    }     return 0; }

Build the code

As promised, here's the complete code for the working application.

To build this example

Delete any code you've entered in HelloWindowsDesktop.cpp in the editor. Copy this example code and then paste it into HelloWindowsDesktop.cpp:

                // HelloWindowsDesktop.cpp // compile with: /D_UNICODE /DUNICODE /DWIN32 /D_WINDOWS /c  #include <windows.h> #include <stdlib.h> #include <string.h> #include <tchar.h>  // Global variables  // The main window class name. static TCHAR szWindowClass[] = _T("DesktopApp");  // The string that appears in the application's title bar. static TCHAR szTitle[] = _T("Windows Desktop Guided Tour Application");  HINSTANCE hInst;  // Forward declarations of functions included in this code module: LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);  int WINAPI WinMain(    _In_ HINSTANCE hInstance,    _In_opt_ HINSTANCE hPrevInstance,    _In_ LPSTR     lpCmdLine,    _In_ int       nCmdShow ) {    WNDCLASSEX wcex;     wcex.cbSize = sizeof(WNDCLASSEX);    wcex.style          = CS_HREDRAW | CS_VREDRAW;    wcex.lpfnWndProc    = WndProc;    wcex.cbClsExtra     = 0;    wcex.cbWndExtra     = 0;    wcex.hInstance      = hInstance;    wcex.hIcon          = LoadIcon(wcex.hInstance, IDI_APPLICATION);    wcex.hCursor        = LoadCursor(NULL, IDC_ARROW);    wcex.hbrBackground  = (HBRUSH)(COLOR_WINDOW+1);    wcex.lpszMenuName   = NULL;    wcex.lpszClassName  = szWindowClass;    wcex.hIconSm        = LoadIcon(wcex.hInstance, IDI_APPLICATION);     if (!RegisterClassEx(&wcex))    {       MessageBox(NULL,          _T("Call to RegisterClassEx failed!"),          _T("Windows Desktop Guided Tour"),          NULL);        return 1;    }     // Store instance handle in our global variable    hInst = hInstance;     // The parameters to CreateWindowEx explained:    // WS_EX_OVERLAPPEDWINDOW : An optional extended window style.    // szWindowClass: the name of the application    // szTitle: the text that appears in the title bar    // WS_OVERLAPPEDWINDOW: the type of window to create    // CW_USEDEFAULT, CW_USEDEFAULT: initial position (x, y)    // 500, 100: initial size (width, length)    // NULL: the parent of this window    // NULL: this application does not have a menu bar    // hInstance: the first parameter from WinMain    // NULL: not used in this application    HWND hWnd = CreateWindowEx(       WS_EX_OVERLAPPEDWINDOW,       szWindowClass,       szTitle,       WS_OVERLAPPEDWINDOW,       CW_USEDEFAULT, CW_USEDEFAULT,       500, 100,       NULL,       NULL,       hInstance,       NULL    );     if (!hWnd)    {       MessageBox(NULL,          _T("Call to CreateWindow failed!"),          _T("Windows Desktop Guided Tour"),          NULL);        return 1;    }     // The parameters to ShowWindow explained:    // hWnd: the value returned from CreateWindow    // nCmdShow: the fourth parameter from WinMain    ShowWindow(hWnd,       nCmdShow);    UpdateWindow(hWnd);     // Main message loop:    MSG msg;    while (GetMessage(&msg, NULL, 0, 0))    {       TranslateMessage(&msg);       DispatchMessage(&msg);    }     return (int) msg.wParam; }  //  FUNCTION: WndProc(HWND, UINT, WPARAM, LPARAM) // //  PURPOSE:  Processes messages for the main window. // //  WM_PAINT    - Paint the main window //  WM_DESTROY  - post a quit message and return LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam) {    PAINTSTRUCT ps;    HDC hdc;    TCHAR greeting[] = _T("Hello, Windows desktop!");     switch (message)    {    case WM_PAINT:       hdc = BeginPaint(hWnd, &ps);        // Here your application is laid out.       // For this introduction, we just print out "Hello, Windows desktop!"       // in the top left corner.       TextOut(hdc,          5, 5,          greeting, _tcslen(greeting));       // End application-specific layout section.        EndPaint(hWnd, &ps);       break;    case WM_DESTROY:       PostQuitMessage(0);       break;    default:       return DefWindowProc(hWnd, message, wParam, lParam);       break;    }     return 0; }

On the Build menu, choose Build Solution. The results of the compilation should appear in the Output window in Visual Studio.
To run the application, press F5. A window that contains the text "Hello, Windows desktop!" should appear in the upper-left corner of the display.